Difference between HTTP1.1 vs HTTP2

The Beginning of HTTP: Version 0.9 & 1.0

In the earliest phase (HTTP/0.9), the HTTP protocol did not use headers and only transmitted plain HTML files. It was a one-line protocol only supporting the GET method.

As the need to exchange more than just plain HTML emerged along with the client and server applications becoming more mature, HTTP/1.0 (between 1991–1996) introduced several new features.

HTTP/1.1

HTTP/1.1, the first standardized version of HTTP, was introduced in 1997. It presented significant performance optimizations (over HTTP/0.9 and HTTP/1.0) and transformed the way requests and responses were exchanged between clients and servers.This is the Protocol Serving Netizens for Over 15 Years.

The Protocol Designed to Speed Up Today’s Complex Web pages: HTTP/2

At the beginning of 2010, Google introduced an experimental protocol, SPDY, which supported multiplexing (multiple requests/responses sent and received asynchronously over a single TCP connection) but as it gained traction IETF’s HTTP Working Group came up with HTTP/2 in 2015, which is based on the SPDY protocol.

Key Features of HTTP/2:

• Single Connection. Only one connection to the server is used to load a website, and that connection remains open as long as the website is open. This reduces the number of round trips needed to set up multiple TCP connections.
• Multiplexing. Multiple requests are allowed at the same time, on the same connection. Previously, with HTTP/1.1, each transfer would have to wait for other transfers to complete.
• Server Push. Additional resources can be sent to a client for future use.
• Prioritization. Requests are assigned dependency levels that the server can use to deliver higher priority resources faster.
• Binary. Makes HTTP/2 easier for a server to parse, more compact, and less error-prone. No additional time is wasted translating information from text to binary, which is the computer’s native language.
• Header Compression. HTTP/2 uses HPACK compressions, which reduces overhead. Many headers were sent with the same values in every request in HTTP/1.1.